Here, by an “LED assembly” is meant quite generally an LED (light-emitting diode) or a group (array) of LEDs, in any desired arrangement, such as square, circular or linear, wherein the assembly conventionally comprises a substrate and a housing. In the present case this assembly is preassembled on a printed circuit board. Here, by this “printed circuit board” is meant quite generally a substrate or component, made for example of FR4, ceramic but also aluminum etc., that carries printed conductors.
It is known for LED assemblies to be preassembled on printed circuit boards and then attached to a carrier body or lead frame, usually a heat sink, for example to keep the temperature of the LED assembly at a suitable value during operation. Such LED assemblies are increasingly being used in motor vehicles, where they are used in a luminaire housing, for example for headlamps, but also for tail lights, brake lights, indicator lights etc., but also quite generally in lighting engineering or light control devices.
From DE 199 09 399 C1 for example a partially flexible multiple LED assembly for stepped mounting in a luminaire housing of a motor vehicle is known.
One problem when mounting LED assemblies is that in the respective luminaire housing or the like they have to be positioned on the carrier body with great accuracy in order to achieve an optimum luminous efficiency in the desired emission direction. Difficulties are presented here by the high number of degrees of freedom when positioning the LED assemblies, an added problem being that the LED assembly is preassembled on a printed-circuit board; in the case of this mounting, as tests have revealed, relatively large tolerances exist. As has been demonstrated in practice, it is therefore not enough for the printed-circuit board itself to be positioned on the carrier body or heat sink exactly, for example by means of centering pins on the heat sink and centering holes in the printed-circuit board, rather the LED assembly has to be adjusted exactly relative to the carrier body or heat sink. Without exact positioning the desired high luminous efficiency of the LED assembly is not possible as the positioning tolerances lead to high light depreciation, or the light for example cannot be launched correctly in a fiber-optic conductor.